Isoalloxazine
{{Chembox
| ImageFile = Alloxazine.svg
| ImageSize = 200px
| IUPACName = 1H-benzo[g]pteridine-2,4-dione
| OtherNames = 1,2,3,4-Tetrahydrobenzopteridine-2,4-dione; Benzo(g)pteridine-2,4(1H,3H)-dione
| Section1 = {{Chembox Identifiers
| CASNo = 490-59-5
| Beilstein = 85819
| ChEBI = 37325
| ChEMBL = 68500
| ChemSpiderID = 4522915
| DrugBank =
| EINECS = 207-714-3
| IUPHAR_ligand = 456
| StdInChI = 1S/C10H6N4O2/c15-9-7-8(13-10(16)14-9)12-6-4-2-1-3-5(6)11-7/h1-4H,(H2,12,13,14,15,16)
| StdInChIKey = HAUGRYOERYOXHX-UHFFFAOYSA-N
| KEGG =
| MeSHName =
| PubChem = 5372720
| UNII = 880W3VF9YW
| SMILES = C1=CC=C2C(=C1)N=C3C(=N2)NC(=O)NC3=O
}}
| Section2 = {{Chembox Properties
| C=10 | H=6 | N=4 | O=2
| Appearance = Red solid
| Density =
| MeltingPtC = 200
| BoilingPt =
| Solubility =
}}
| Section3 = {{Chembox Hazards
| MainHazards =
| FlashPt =
| AutoignitionPt =
}}
}}
Isoalloxazine is the structural foundation of flavins such as riboflavin (vitamin B2) and is a heterocyclic compound.{{cite web |url=https://medical-dictionary.thefreedictionary.com/isoalloxazine/ |title=isoalloxazine |author= |date=2012 |website=Farlex Partner Medical Dictionary |access-date=November 25, 2022}} It has a tricyclic structure which means it has three interconnected rings of atoms and is a tautomer of alloxazine.{{cite journal |last1=Berezovskii |first1=VM |last2=Eremenko |first2=TV |date=1963 |title=Chemistry of Alloxazines and Isoalloxazines |url=https://iopscience.iop.org/article/10.1070/RC1963v032n06ABEH001343 |journal=Russian Chemical Reviews |volume=32 |issue=6 |pages=290–307 |doi=10.1070/RC1963v032n06ABEH001343 |access-date=November 23, 2022}} The structure is formed by primary-secondary aromatic o-diamines and they are a high-melting crystalline substance. The R-group is used to attach various flavin groups It has a similar structure to pteridines which has two interconnected rings. Isoalloxazine was first obtained in 1934 by Richard Kuhn an Austrian-German biochemist and lab mates. File:Isoalloxazine Structure.png
Isoalloxazine ring
Isoalloxazine rings can exist in different redox and ionization states depending on the chemistry of FMN and FAD associated with it.{{cite book |last1=Luliano |first1=James N. |title=New Approaches for Flavin Catalysis |chapter=Vibrational spectroscopy of flavoproteins |series=Methods in Enzymology |date=2019 |volume=620 |publisher=Elsevier Inc |location=Methods in Enzymology |issn=0076-6879 |pages=189–214 |doi=10.1016/bs.mie.2019.03.011 |pmid=31072487 |isbn=9780128168295 |s2cid=146800749 |edition=volume 620 |chapter-url=https://doi.org/10.1016/bs.mie.2019.03.011}} Using the redox-active isoalloxazine system, FAD and FMN are able to do one and two electron transfer reactions and also be coupled with proton transfers.{{cite journal |last1=Aleksandrov |first1=Alexey |title=A Molecular Mechanics Model for Flavins |journal=Journal of Computational Chemistry |date=2019 |volume=40 |issue=32 |pages=2834–2842 |doi=10.1002/jcc.26061 |pmid=31471978 |s2cid=201730443 |url=https://pubmed.ncbi.nlm.nih.gov/31471978/}}
